Abstract: :
Purpose: To evaluate the effects of a single oral dose of nimodipine(a calcium channel blocker with central activity) or placeboon retinal microcirculation, standard automated perimetry (SAP)and plasma levels of endothelin–1 (ET–1) in a cohortof patients previously shown to have a large increase in plasmaET–1 following a cold provocation test.Methods: 10 open–angle glaucoma patients were randomizedto receive a single dose of either nimodipine (60 mg) or placebo,two hours prior to the study visit. Baseline pre–coolingmeasurements consisted of SAP examination (24–2 SITA programof the Humphrey Field Analyzer), scanning laser Doppler flowmetry(SLDF) of the peripapillary retina (Heidelberg Retina Flowmeter)and pulsatile ocular blood flow (POBF) measurements. After 30minutes of a cold provocative test, administered via a head–vestcooling garment containing coolant fluid, the same tests wererepeated. Blood was collected before and after cooling and plasmaET–1 was determined by immunoassay. Blood pressure, pulse,finger flow measurements and skin temperature were monitoredduring the experiment. SAP, SLDF and POBF tests were repeatedone week later in a recovery visit. After one month, patientswere crossed–over to the other treatment arm and the proceduresas described above were repeated. A group comparison of pre–coolingmeasurements and the effect of cooling in each group were analysed.Results: No significant differences were observed followingnimodipine or placebo between baseline pre–cooling visualfield indices (MD and PSD), SLDF measurements, POBF values,plasma ET–1, blood pressure and pulse (p > 0.5). Aftercold provocation test, no significant changes were observedin SLDF and POBF measurements, visual field indices or plasmaET–1, either in the nimodipine or placebo arms (p >0.2). The average percentage increase in plasma ET–1 aftercooling was 12 and 18% following nimodipine or placebo respectively(p = 0.7).Conclusions: Following a single dose of nimodipine, no significantchanges were observed in retinal microcirculation, POBF, visualfield function or plasma ET–1 levels, either at baselineor following a cold provocation test.